Semiconductor device and manufacturing method of the same

ABSTRACT

Disclosed herein is a semiconductor device including: a substrate having a first conductive layer and a second conductive layer arranged deeper than the first conductive layer; a large-diameter concave portion having, on a main side of a substrate, an opening sized to overlap the first and second conductive layers, with the first conductive layer exposed in part of the bottom of the large-diameter concave portion; a small-diameter concave portion extended from the large-diameter concave portion and formed by digging into the bottom of the large-diameter concave portion, with the second conductive layer exposed at the bottom of the small-diameter concave portion; and a conductive member provided in a connection hole made up of the large- and small-diameter concave portions to connect the first and second conductive layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/494,134, filed Sep. 23, 2014, which is a continuation of Ser. No.13/617,806, filed Sep. 14, 2012, now U.S. Pat. No. 8,871,633, whichclaims priority to Japanese Patent Application No. JP 2011-219843, filedin the Japan Patent Office on Oct. 4, 2011, the entire disclosures ofwhich are hereby incorporated herein by reference.

BACKGROUND

The present technology relates to a semiconductor device havingconductive layers of different heights exposed in a connection hole anda manufacturing method of the same.

LSIs and other semiconductor devices have downsized and grown insophistication thanks to high-density integration made possible by microfabrication process. In such a high-density integrated semiconductordevice, new ideas have been introduced to reduce the necessary area ofthe interlayer connection structure for multilayer interconnects. Forexample, Japanese Patent Laid-Open No. 1997-199586 discloses asemiconductor device having a shared contact structure. In thissemiconductor device, the conductive material layers of differentheights are connected together with a single connection hole forinterlayer connection between multilayer interconnects. As a result, ashared contact structure ensures a smaller necessary area than when aconnection hole is provided for each conductive material layer, thusproviding high-density integration.

The step of making a connection hole in a shared contact structure isperformed as described below. First, a resist pattern having an openingpattern overlapping both of the conductive material layers of differentheights is formed by lithography. Next, the interlayer insulating filmis etched using the resist pattern as a mask until the shallowconductive material layer is exposed. Next, the surrounding interlayerinsulating film is etched using the already-exposed and shallowconductive material layer as a mask until the deep conductive materiallayer is exposed. The interlayer insulating film is etched as describedabove using a single resist pattern, thus forming a shared contactstructure with different conductive material layers exposed in aconnection hole.

SUMMARY

However, the step of making a connection hole in a shared contactstructure in related art causes the shallow conductive material layerthat is exposed earlier to be subjected to plasma for an extended periodof time during etching of the interlayer insulating film, thus resultingin overetching of the shallow conductive material layer. This leads toformation of a metal-based deposit on the side wall of the connectionhole. This metal-based deposit remains unremoved after asking orchemical posttreatment, producing particles and resulting in loweryield. Further, this excessive etching of the shallow conductivematerial layer may give rise to a complete penetration of the conductivematerial layer. In this case, when the final metal is filled into theconnection hole, the metal can come into contact with only the lateralside of the conductive material layer, thus resulting in increasedelectrical resistance.

In light of the foregoing, it is desirable to provide a semiconductordevice having conductive material layers of different heights exposed ina connection hole. The semiconductor device offers improved yield byminimizing excessive etching of the shallow conductive material layer.It is also desirable to provide a manufacturing method of the same.

According to an embodiment of the present technology, there is provideda semiconductor device including a substrate and connection hole. Thesubstrate has a first conductive layer and a second conductive layerarranged deeper than the first conductive layer. The connection hole ismade up of a large-diameter concave portion and small-diameter concaveportion. The large-diameter concave portion has an opening sized tooverlap the first and second conductive layers on a main side of asubstrate. The first conductive layer is exposed in part of the bottomof the large-diameter concave portion. The small-diameter concaveportion is extended from the large-diameter concave portion and formedby digging into the bottom of the large-diameter concave portion. Thesecond conductive layer is exposed at the bottom of the small-diameterconcave portion. A conductive member adapted to connect the first andsecond conductive layers is provided in the connection hole made up ofthe large- and small-diameter concave portions.

Further, the present technology is also a manufacturing method of thesemiconductor device configured as described above and includes thefollowing steps. A large-diameter resist pattern is formed on asubstrate incorporating a first conductive layer and a second conductivelayer arranged deeper than the first conductive layer. Thelarge-diameter resist pattern has an opening that exposes the tops ofthe first and second conductive layers. A large-diameter concave portionhaving the first conductive layer exposed at the bottom is formed in thesubstrate based on etching using this large-diameter resist pattern as amask. A small-diameter resist pattern is formed on the substrate. Thesmall-diameter resist pattern has an opening that exposes the top of thesecond conductive layer within the area where the large-diameter concaveportion is formed. A small-diameter concave portion having the secondconductive layer exposed at the bottom is formed in the substrate basedon etching using this small-diameter resist pattern as a mask. Thesemiconductor device configured as described above is acquired by theabove steps.

In the semiconductor device configured as described above and themanufacturing method thereof, etching is performed using the large- andsmall-diameter resist patterns as masks during the formation of thelarge- and small-diameter concave portions making up the connectionhole. As a result, the first and second conductive layers arranged atdifferent depths are exposed in the connection hole. At this time,etching is performed using the unique small-diameter resist patterncovering the first conductive layer as a mask rather than using thefirst conductive layer exposed at the bottom of the large-diameterconcave portion as a mask. This minimizes excessive subjection of thefirst conductive layer to an etching atmosphere for an extended periodof time, thus preventing excessive etching of the same layer.

Thus, the present technology prevents excessive etching of the firstconductive layer arranged shallower than the second conductive layerduring the formation of the connection hole in which the first andsecond conductive layers arranged at different depths are exposed. Thisprevents thinning of the first conductive layer caused by excessiveetching, thus providing proper conductivity of the first conductivelayer and proper connection between the same layer and filling member.As a result, it is possible to achieve improved yield of thesemiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of main components of a semiconductordevice according to a first embodiment;

FIGS. 2A to 2G are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to the firstembodiment;

FIGS. 3A to 3G are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to a secondembodiment;

FIGS. 4A to 4G are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to a thirdembodiment;

FIGS. 5A to 5H are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to a fourthembodiment;

FIGS. 6A to 6F are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to a fifthembodiment;

FIGS. 7A to 7F are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to a sixthembodiment; and

FIGS. 8A to 8F are cross-sectional process diagrams illustrating themanufacturing method of the semiconductor device according to a seventhembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will be given below of the preferred embodiments of thepresent technology. It should be noted that the description will begiven in the following order.

-   1. First embodiment (configuration of the semiconductor device)-   2. First embodiment (manufacturing method in which the first    interconnect exposed at the bottom of the large-diameter concave    portion formed earlier is covered with the small-diameter resist    pattern)-   3. Second embodiment (manufacturing method in which etching is    stopped halfway in such a manner that the unetched thicknesses on    top of the first and second interconnects agree)-   4. Third embodiment (manufacturing method in which etching is    stopped halfway using the interlayer insulating film as an etching    stopper)-   5. Fourth embodiment (manufacturing method in which the filling    member is filled into the concave portion formed by stopping etching    halfway)-   6. Fifth embodiment (manufacturing method in which a resist material    used to cover the second interconnect is left unremoved in the    small-diameter concave portion formed earlier)-   7. Sixth embodiment (manufacturing method in which etching is    stopped halfway in such a manner that the unetched thicknesses on    top of the first and second interconnects agree)-   8. Seventh embodiment (manufacturing method in which etching is    stopped halfway in such a manner that the unetched thicknesses on    top of the first and second interconnects agree and in which a hard    mask is used)

It should be noted that like components in the embodiments andmodification examples will be denoted by the same reference numerals,and the description thereof will be omitted.

1. First Embodiment (Configuration of the Semiconductor Device)

FIG. 1 is a cross-sectional view of main components of a semiconductordevice according to a first embodiment. A detailed description will begiven below of the semiconductor device according to the firstembodiment based on this cross-sectional view of main components.

A semiconductor device 1 shown in FIG. 1 includes a substrate made up ofa first substrate 10 and second substrate 20 that are bonded togetherwith a joint section 30. The first substrate 10 incorporates a firstinterconnect 12, and the second substrate 20 a second interconnect 22.Further, the first interconnect 12 of the first substrate 10 and thesecond interconnect 22 of the second substrate 20 are connected togethervia a connection hole 40 that penetrates the first substrate 10. Itshould be noted that the first and second interconnects are one form ofconductive layers. The structure and fabrication method of theconnection hole 40 are a distinctive feature of the first embodiment. Adetailed description will be given below of the configuration of thesemiconductor device 1, with the first substrate 10, second substrate 20and joint section 30 described in this order.

[First Substrate 10]

The first substrate 10 includes a semiconductor layer 11 and aninterconnect layer 13 that is deposited on the side of the secondsubstrate 20.

The semiconductor layer 11 is a thinned semiconductor substrate made,for example, of single crystalline silicon. Transistor sources anddrains that are not illustrated here are, for example, provided on theside of the semiconductor layer 11 interfacing with the interconnectlayer 13.

Transistor gate electrodes that are not illustrated here are, forexample, provided on the side of the interconnect layer 13 interfacingwith the semiconductor layer 11. These electrodes are covered with aninterlayer insulating film 14 made, for example, of silicon oxide. Aplurality of filled interconnects, each made, for example, of copper,are provided in the groove pattern of the interlayer insulating film 14.One of the plurality of filled interconnects is the first interconnect(first conductive layer) 12. Although not illustrated here, on the otherhand, some of the filled interconnects are connected to the transistorsources and drains and gate electrodes. It should be noted that theinterconnect layer 13 may have a multilayer interconnect structure. Inthis case, the first interconnect 12 may be provided in a layer of anydepth.

[Second Substrate 20]

The second substrate 20 includes a semiconductor layer 21 and aninterconnect layer 23 that is deposited on the side of the firstsubstrate 10.

The semiconductor layer 21 is a thinned semiconductor substrate made,for example, of single crystalline silicon. Transistor sources anddrains that are not illustrated here are, for example, provided on theside of the semiconductor layer 21 interfacing with the interconnectlayer 23.

Transistor gate electrodes that are not illustrated here are, forexample, provided on the side of the interconnect layer 23 interfacingwith the semiconductor layer 21. These electrodes are covered with aninterlayer insulating film 24 made, for example, of silicon oxide. Aplurality of filled interconnects, each made, for example, of copper,are provided in the groove pattern of the interlayer insulating film 24.One of the plurality of filled interconnects is the second interconnect(second conductive layer) 22. Although not illustrated here, on theother hand, some of the filled interconnects are connected to thetransistor sources and drains and gate electrodes. It should be notedthat the interconnect layer 23 may have a multilayer interconnectstructure. In this case, the second interconnect 22 may be provided in alayer of any depth.

Further, through-vias 25 penetrating the semiconductor layer 21 areprovided in the second substrate 20 and connected to some of the filledinterconnects in the interconnect layer 23. The through-vias 25 aremade, for example, of copper.

[Joint Section 30]

The joint section 30 is made of an adhesive film bonding the first andsecond substrates 10 and 20 together. The first and second substrates 10and 20 are bonded together with the joint section 30 sandwiched betweenthe interconnect layer 13 of the first substrate 10 and the interconnectlayer 23 of the second substrate 20.

[Connection Hole 40]

The connection hole 40 is provided to penetrate the first substrate 10and joint section 30 with the first and second interconnects 12 and 22exposed at its bottom. The connection hole 40 configured as describedabove includes a large-diameter concave portion 41 and a small-diameterconcave portion 42. The small-diameter concave portion 42 is extendedfrom the large-diameter concave portion 41 and formed by further digginginto the bottom of the same portion 41.

The opening of the large-diameter concave portion 41 is provided on theexposed side of the semiconductor layer (hereinafter referred to as afront surface 11 a) and sized to overlap the first and secondinterconnects 12 and 22. That is, it is only necessary for the openingof the large-diameter concave portion 41 to be sized to cover thecontact portions of the first and second interconnects 12 and 22 andpartially overlap the first and second interconnects 12 and 22 when thesubstrate is seen in plan view. On the other hand, a depth t1 of thelarge-diameter concave portion 41 is measured from the front surface 11a to the first interconnect 12. The depth t1 may be a depth overetchedto some extent into the first interconnect 12. The interlayer insulatingfilm 14 is exposed together with the first interconnect 12 at the bottomof the large-diameter concave portion 41 located at the depth t1.Further, the opening of the small-diameter concave portion 42 isprovided at the bottom thereof. That is, the bottom of thelarge-diameter concave portion 41 located at the depth t1 includes thefirst interconnect 12 and interlayer insulating film 14.

On the other hand, the small-diameter concave portion 42 is extendedfrom the large-diameter concave portion 41 and formed by digging intothe bottom of the same portion 41. A depth t2 of the small-diameterconcave portion 42 is measured from the bottom of the large-diameterconcave portion 41 to the second interconnect 22. The secondinterconnect 22 is exposed at the bottom of the small-diameter concaveportion 42. It should be noted that the interlayer insulating film 24may be exposed together with the second interconnect 22 at the bottom ofthe small-diameter concave portion 42.

As described above, the bottom of the connection hole 40 located at thedepth t1 includes not only the first interconnect 12 but also theinterlayer insulating film 14 rather than only the first interconnect12.

Further, a conductive member 43 is provided in the connection hole 40 toconnect the first and second interconnects 12 and 22. That is, theconductive member 43 connects the first and second interconnects 12 and22 that are exposed at different depths. Among materials that can beused as the conductive member 43 are a filling metal filled into theconnection hole 40 and a conductive film provided on the inner wall ofthe connection hole 40.

Advantageous Effect of the Semiconductor Device According to the FirstEmbodiment

The semiconductor device 1 according to the first embodiment describedabove has the interlayer insulating film 14 exposed together with thefirst interconnect 12 at the bottom located at the depth t1 of theconnection hole 40. That is, the small-diameter concave portion 42making up the connection hole 40 is formed by etching using a uniquepattern as a mask rather than using the first interconnect 12 exposed atthe bottom of the large-diameter concave portion 41 as a mask.

As will be described in detail thereafter in the embodiments of themanufacturing method, therefore, the semiconductor device 1 includes theconnection hole 40 adapted to prevent excessive etching of the firstinterconnect 12 that is exposed at the depth t1, thus preventing defectscaused by this excessive etching and providing improved yield.

2. First Embodiment (Manufacturing Method in Which the FirstInterconnect Exposed at the Bottom of the Large-Diameter Concave PortionFormed Earlier is Covered with the Small-Diameter Resist Pattern)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to the first embodiment described abovewith reference to the cross-sectional process diagrams shown in FIGS. 2Ato 2G.

As illustrated in FIG. 2A, the first and second substrates 10 and 20 arefabricated. The interconnect layer 13 including the first interconnect12 is provided on one of the main sides of the semiconductor layer 11 ofthe first substrate 10. The interconnect layer 23 including the secondinterconnect 22 is provided on one of the main sides of thesemiconductor layer 21 of the second substrate 20. The first and secondsubstrates 10 and 20 are bonded together with the joint section 30sandwiched between the interconnect layer 13 and interconnect layer 23,thus fabricating a bonded substrate.

It should be noted that the steps up to this point are not particularlylimited and may be performed using ordinary techniques. The steps offorming a connection hole from this point onward are a distinctivefeature of the first embodiment.

As illustrated in FIG. 2B, a large-diameter resist pattern 100 is formedon the exposed side of the semiconductor layer 11 (front side 11 a) ofthe fabricated bonded substrate. The large-diameter resist pattern 100has an opening 100 a that exposes the tops of the first and secondinterconnects 12 and 22. That is, the opening 100 a is formed where thecontact portions of the first and second interconnects 12 and 22 arecovered when the semiconductor layer 11 is seen in plan view from theside of the front side 11 a.

As illustrated in FIG. 2C, the large-diameter concave portion 41 isformed in the bonded substrate by etching using the large-diameterresist pattern 100 as a mask. At this time, the semiconductor layer 11is etched using the large-diameter resist pattern 100 as a mask,followed by etching of the interlayer insulating film 14 until the firstinterconnect 12 is exposed. The etching is terminated when the firstinterconnect 12 is detected. Here, etching is performed using CF₄/Ar orCF₄/Ar/O₂ as an etching gas. However, the etching gas is not limitedthereto. After the etching, the large-diameter resist pattern 100 isremoved.

As a result of the above, the large-diameter concave portion 41 isformed which has an opening sized to overlap the first and secondinterconnects 12 and 22, with the first interconnect 12 exposed in partof the bottom.

As illustrated in FIG. 2D, a new small-diameter resist pattern 102 isformed on the front side 11 a of the semiconductor layer 11. Thesmall-diameter resist pattern 102 has an opening 102 a that does notoverlap the first interconnect 12 but exposes the top of the secondinterconnect 22 within the area where the large-diameter concave portion41 is formed in the bonded substrate. That is, the small-diameter resistpattern 102 fully covers the first interconnect 12 that is exposed atthe bottom of the large-diameter concave portion 41. On the other hand,the opening 102 a formed in the small-diameter resist pattern 102exposes the interlayer insulating film 14 located above the secondinterconnect 22.

As illustrated in FIG. 2E, the small-diameter concave portion 42 isformed at the bottom of the large-diameter concave portion 41 by etchingusing the small-diameter resist pattern 102 as a mask. At this time, theinterlayer insulating film 14 is etched by using the small-diameterresist pattern 102 covering the first interconnect 12 as a mask,followed by etching of the joint section 30. The etching is terminatedwhen the second interconnect 22 is detected. Here, etching is performedusing CF₄/Ar or CF₄/Ar/O₂ as an etching gas. However, the etching gas isnot limited thereto.

As a result of the above, the small-diameter concave portion 42 isformed which is extended from the large-diameter concave portion 41 andformed by digging into the bottom of the large-diameter concave portion42. The second interconnect 22 is exposed at the bottom of thesmall-diameter concave portion 42.

As illustrated in FIG. 2F, the resist pattern (102) is removed. Thiscompletes the fabrication of the connection hole 40 having the first andsecond interconnects 12 and 22 exposed at its bottom.

As illustrated in FIG. 2G, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40. As a result, the semiconductor device 1according to the first embodiment described with reference to FIG. 1 isacquired.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the First Embodiment

In the manufacturing method according to the first embodiment describedabove, etching is performed using the large-diameter resist pattern 100and small-diameter resist pattern 102 as masks respectively to form thepatterns of the large-diameter concave portion 41 and small-diameterconcave portion 42. When the pattern of the small-diameter concaveportion 42 is formed, etching is performed using the uniquesmall-diameter resist pattern 102 covering the first interconnect 12 asa mask rather than using the first interconnect 12 exposed at the bottomof the large-diameter concave portion 41 as a mask. This preventsexcessive subjection of the first interconnect 12 to an etchingatmosphere.

Therefore, the manufacturing method according to the first embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

This contributes to improved yield of the semiconductor device 1.

Further, etching is performed using two resist patterns, one for thelarge-diameter concave portion 41 and another for the small-diameterconcave portion 42. Therefore, a thinner resist film is enough, which isnot the case for etching using a single resist pattern all the waythrough the process. This provides improved patterning accuracy of theresist pattern used to form the connection hole 40, thus contributing topitch reduction in the semiconductor device.

3. Second Embodiment (Manufacturing Method in Which Etching is StoppedHalfway in Such a Manner that the Unetched Thicknesses on Top of theFirst and Second Interconnects Agree)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to a second embodiment with referenceto the cross-sectional process diagrams shown in FIGS. 3A to 3G. Itshould be noted that the final configuration of the semiconductor device1 is the same as that of the semiconductor device 1 according to thefirst embodiment.

First, a bonded substrate is fabricated which has the first and secondsubstrates 10 and 20 bonded together with the joint section 30sandwiched therebetween. The steps of forming the connection hole 40thereafter are a distinctive feature of the second embodiment.

Next, as illustrated in FIG. 3A, a hard mask layer 200 is formed on thefront side 11 a of the semiconductor layer 11 of the fabricated bondedsubstrate. The hard mask layer 200 is made of a material such astitanium nitride (TiN) to which particles caused by etching do notreadily adhere. Further, the large-diameter resist pattern 100 havingthe opening 100 a is formed on the hard mask layer 200. The opening 100a exposes the tops of the first and second interconnects 12 and 22.

As illustrated in FIG. 3B, the hard mask layer 200 is etched using thelarge-diameter resist pattern 100 as a mask, thus forming a hard mask200 a. Next, the semiconductor layer 11 is etched using thelarge-diameter resist pattern 100 as a mask, thus forming the pattern ofa large-diameter concave portion 41-2 on the bonded substrate. At thistime, the etching of the semiconductor layer 11 is terminated before thefirst interconnect 12 is reached, thus leaving the semiconductor layer11 and interlayer insulating film 14 unremoved on top of the firstinterconnect 12. Here, for example, the hard mask layer 200 made oftitanium nitride (TiN) is etched using Cl₂/BCl₃ as an etching gas, andthe semiconductor layer 11 made of silicon (Si) is etched using Cl₂/O₂as an etching gas. After the etching, the large-diameter resist pattern100 is removed.

As a result of the above, the large-diameter concave portion 41-2 isformed which has an opening sized to overlap the first and secondinterconnects 12 and 22, with an unetched thickness ‘a’ remainingunremoved on top of the first interconnect 12.

As illustrated in FIG. 3C, the small-diameter resist pattern 102 isformed anew on the hard mask 200 a. The small-diameter resist pattern102 has the opening 102 a that does not overlap the first interconnect12 but exposes the top of the second interconnect 22 within the areawhere the large-diameter concave portion 41-2 is formed in the bondedsubstrate.

As illustrated in FIG. 3D, the pattern of a small-diameter concaveportion 42-2 is formed at the bottom of the large-diameter concaveportion 41-2 by etching using the small-diameter resist pattern 102 as amask. At this time, the semiconductor layer 11, interlayer insulatingfilm 14 and joint section 30 are etched in this order using thesmall-diameter resist pattern 102 as a mask, and the etching isterminated before the second interconnect 22 is reached. Here, etchingis performed until the unetched thickness ‘a’ on top of the firstinterconnect 12 and an unetched thickness ‘b’ on top of the secondinterconnect 22 agree (i.e., a=b). For example, an etching time thatprovides a=b is specified in advance, and the etching is terminated whenthis period of time elapses.

As illustrated in FIG. 3E, the resist pattern (102) is removed. As aresult, the hard mask 200 a is provided on the front side 11 a of thesemiconductor layer 11. The same mask 200 has the large-diameter concaveportion 41-2 whose depth does not expose the first interconnect 12 andthe small-diameter concave portion 42-2 whose depth does not expose thesecond interconnect 22 and is aligned with the opening of thelarge-diameter concave portion 41-2. In this condition, the unetchedthickness ‘a’ on top of the first interconnect 12 and the unetchedthickness ‘b’ on top of the second interconnect 22 agree (i.e., a=b).

As illustrated in FIG. 3F, the bottoms of the large- and small-diameterconcave portions 41-2 and 42-2 are dug at the same time by etching fromabove the hard mask 200 a. At this time, the semiconductor layer 11,interlayer insulating film 14 and joint section 30 are etched until bothof the first and second interconnects 12 and 22 are exposed. Here,etching is performed under the conditions that allow digging of thesemiconductor layer 11, interlayer insulating film 14 and joint section30 at the same etch rate. For example, etching is performed using CF₄/Aror CF₄/Ar/O₂ as an etching gas. After the etching, the hard mask 200 ais removed as necessary. This completes the fabrication of theconnection hole 40 having the first and second interconnects 12 and 22exposed at its bottom.

As illustrated in FIG. 3G, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40.

As a result of the above steps, the manufacture of the semiconductordevice 1 according to the second embodiment is complete.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the Second Embodiment

In the manufacturing method according to the second embodiment describedabove, the large- and small diameter concave portions 41-2 and 42-2 areformed first in such a manner that the small diameter concave portion42-2 is extended from the bottom of the large-diameter concave portion41-2 without exposing the first and second interconnects 12 and 22 asillustrated in FIG. 3E. At this time, etching is performed so that theunetched thickness ‘a’ on top of the first interconnect 12 and theunetched thickness ‘b’ on top of the second interconnect 22 agree (i.e.,a=b). In this condition, the semiconductor layer 11, interlayerinsulating film 14 and joint section 30 are etched at the same etchrate. As a result, the etching is terminated when the secondinterconnect 22 is exposed simultaneously with the exposure of the firstinterconnect 12. This ensures that the exposed first interconnect 12 isnot subjected to an etching atmosphere for an extended period of time.

Therefore, the manufacturing method according to the second embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40as does the manufacturing method according to the first embodiment.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

This contributes to improved yield of the semiconductor device 1.

Still further, in the manufacturing method according to the secondembodiment, the depth of the large-diameter concave portion 41-2 thatdoes not reach the first interconnect 12 is smaller than the depth t1 ofthe large-diameter concave portion 41 having the first interconnect 12exposed at the bottom described with reference to FIG. 1 as illustratedin FIG. 3B.

This particularly contributes to an even thinner resist film of thelarge-diameter resist pattern 100 used to form the pattern of theshallow large-diameter concave portion 41-2, thus providing improvedpatterning accuracy in fabricating the large-diameter resist pattern100.

In addition, as illustrated in FIG. 3C, during the formation of thesmall-diameter resist pattern 102 on the front side 11 a of thesemiconductor layer 11 on which the shallow large-diameter concaveportion 41-2 is formed, the resist film with only a small leveldifference is patterned by photolithography, thus ensuring highpatterning accuracy.

This contributes to further pitch reduction in the semiconductor device.

4. Third Embodiment (Manufacturing Method in Which Etching is StoppedHalfway Using the Interlayer Insulating Film as an Etching Stopper)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to a third embodiment with reference tothe cross-sectional process diagrams shown in FIGS. 4A to 4G. It shouldbe noted that the final configuration of the semiconductor device 1 isthe same as that of the semiconductor device 1 according to the firstembodiment.

First, a bonded substrate is fabricated which has the first and secondsubstrates 10 and 20 bonded together with the joint section 30sandwiched therebetween.

Next, as illustrated in FIG. 4A, the hard mask layer 200 is formed onthe front side 11 a of the semiconductor layer 11 of the fabricatedbonded substrate. Further, the large-diameter resist pattern 100 isformed on the hard mask layer 200. The same pattern 100 has the opening100 a that exposes the tops of the first and second interconnects 12 and22. The steps up to this point are the same as those of themanufacturing method according to the second embodiment. The timingdescribed next when etching is terminated during the formation of thepattern of the large-diameter concave portion is a distinctive featureof the third embodiment.

As illustrated in FIG. 4B, the hard mask layer 200 is etched using thelarge-diameter resist pattern 100 as a mask, thus forming the hard mask200 a. Next, the semiconductor layer 11 is etched under differentetching conditions using the large-diameter resist pattern 100 as amask, thus forming the pattern of a large-diameter concave portion 41-3on the bonded substrate. At this time, the interlayer insulating film 14is used as an etching stopper, and the etching is terminated when thesame film 14 is exposed. This leaves the interlayer insulating film 14unremoved as the unetched thickness ‘a’ on top of the first interconnect12. After the etching, the large-diameter resist pattern 100 is removed.

As a result, the large-diameter concave portion 41-3 is formed which hasan opening sized to overlap the first and second interconnects 12 and 22with its bottom located at the interface between the semiconductor layer11 and interlayer insulating film 14.

As illustrated in FIG. 4C, the small-diameter resist pattern 102 isformed anew on the hard mask 200 a. The small-diameter resist pattern102 has the opening 102 a that does not overlap the first interconnect12 but exposes the top of the second interconnect 22 within the areawhere the large-diameter concave portion 41-3 is formed in the bondedsubstrate.

As illustrated in FIG. 4D, the pattern of a small-diameter concaveportion 42-3 is formed at the bottom of the large-diameter concaveportion 41-3 by etching using the small-diameter resist pattern 102 as amask. At this time, the interlayer insulating film 14 and joint section30 are etched in this order using the small-diameter resist pattern 102as a mask, and the etching is terminated before the second interconnect22 is reached. Here, etching is performed until the unetched thickness‘a’ on top of the first interconnect 12 and the unetched thickness ‘b’on top of the second interconnect 22 agree (i.e., a=b) as in the secondembodiment.

As illustrated in FIG. 4E, the resist pattern (102) is removed. As aresult, the hard mask 200 a is provided which has the large-diameterconcave portion 41-3 whose depth does not expose the first interconnect12 and the small-diameter concave portion 42-3 whose depth does notexpose the second interconnect 22 and which is aligned with the openingof the large-diameter concave portion 41-3 on the front side 11 a of thesemiconductor layer 11. In this condition, the unetched thickness ‘a’ ontop of the first interconnect 12 and the unetched thickness ‘b’ on topof the second interconnect 22 agree (i.e., a=b).

As illustrated in FIG. 4F, the bottoms of the large- and small-diameterconcave portions 41-3 and 42-3 are dug at the same time by etching fromabove the hard mask 200 a. At this time, the interlayer insulating film14 and joint section 30 are etched until both of the first and secondinterconnects 12 and 22 are exposed. Here, etching is performed underthe conditions that allow digging of the interlayer insulating film 14and joint section 30 at the same etch rate. After the etching, the hardmask 200 a is removed as necessary.

This completes the fabrication of the connection hole 40 having thefirst and second interconnects 12 and 22 exposed at its bottom.

As illustrated in FIG. 4G, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40.

As a result of the above steps, the manufacture of the semiconductordevice 1 according to the third embodiment is complete.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the Third Embodiment

In the manufacturing method according to the third embodiment describedabove, the large- and small diameter concave portions 41-3 and 42-3 areformed first in such a manner that the small diameter concave portion42-3 is extended from the bottom of the large-diameter concave portion41-3 without exposing the first and second interconnects 12 and 22 asillustrated in FIG. 4E. At this time, etching is performed so that theunetched thickness ‘a’ on top of the first interconnect 12 and theunetched thickness ‘b’ on top of the second interconnect 22 agree (i.e.,a=b). In this condition, the semiconductor layer 11, interlayerinsulating film 14 and joint section 30 are etched at the same etchrate. As a result, the etching is terminated when the secondinterconnect 22 is exposed simultaneously with the exposure of the firstinterconnect 12. This ensures that the exposed first interconnect 12 isnot subjected to an etching atmosphere for an extended period of time.

Therefore, the manufacturing method according to the third embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40as does the manufacturing method according to the first embodiment.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

Further, in the manufacturing method according to the third embodiment,the interlayer insulating film 14 is used as an etching stopper duringthe formation of a pattern of the large-diameter concave portion 41-3,and the etching is terminated when the same film 14 is exposed asillustrated in FIG. 4B. This makes it possible to terminate etching in awell-controlled manner, thus contributing to improved yield of thesemiconductor device 1.

Still further, the depth of the large-diameter concave portion 41-3 thatdoes not reach the first interconnect 12 is smaller than the depth t1 ofthe large-diameter concave portion 41 having the first interconnect 12exposed at the bottom described with reference to FIG. 1. This providesimproved patterning accuracy in forming the large- and small-diameterresist patterns 100 and 102 as in the second embodiment.

As a result, it is possible to achieve further pitch reduction in thesemiconductor device.

5. Fourth Embodiment (Manufacturing Method in Which the Filling Memberis Filled into the Concave Portion Formed by Stopping Etching Halfway)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to a fourth embodiment with referenceto the cross-sectional process diagrams shown in FIGS. 5A to 5H. Itshould be noted that the final configuration of the semiconductor device1 is the same as that of the semiconductor device 1 according to thefirst embodiment.

First, a bonded substrate is fabricated which has the first and secondsubstrates 10 and 20 bonded together with the joint section 30sandwiched therebetween.

Next, as illustrated in FIG. 5A, the hard mask layer 200 is formed onthe front side 11 a of the semiconductor layer 11 of the fabricatedbonded substrate. A material which will serve as an etching mask for thefilling material formed thereafter is used as the hard mask layer 200.Among materials that can be used as the hard mask layer 200 are titaniumnitride (TiN) and silicon nitride (SiN). Here, silicon nitride (SiN) isused as an example. Next, the large-diameter resist pattern 100 isformed on the hard mask layer 200. The same pattern 100 has the opening100 a that exposes the tops of the first and second interconnects 12 and22.

As illustrated in FIG. 5B, the hard mask layer 200 is etched using thelarge-diameter resist pattern 100 as a mask, thus forming the hard mask200 a. Next, the semiconductor layer 11 is etched using thelarge-diameter resist pattern 100 as a mask, thus forming the pattern ofa large-diameter concave portion 41-4 on the bonded substrate. At thistime, the etching is terminated before the first interconnect 12 isexposed, thus leaving the semiconductor layer 11 and interlayerinsulating film 14 unremoved on top of the first interconnect 12.Although only the interlayer insulating film 14 is left unremoved in theexample shown in FIG. 5B, the semiconductor layer 11 may be leftunremoved together with the interlayer insulating film 14. Here, etchingis performed using Cl₂/O₂ as an etching gas. After the etching, thelarge-diameter resist pattern 100 is removed.

As a result, the large-diameter concave portion 41-4 is formed which hasan opening sized to overlap the first and second interconnects 12 and 22with its bottom located at the interface between the semiconductor layer11 and interlayer insulating film 14.

The steps up to this point are the same as those of the manufacturingmethod according to the third embodiment. The step of filling thelarge-diameter concave portion 41-4 described next is a distinctivefeature of the fourth embodiment.

As illustrated in FIG. 5C, a filling member 400 is filled into thelarge-diameter concave portion 41-4 for planarization. The fillingmember 400 has a high etch selectivity against the hard mask 200 a inthe etching step which will be performed next. Silicon oxide (SiO₂) isamong such a material.

As illustrated in FIG. 5D, the new small-diameter resist pattern 102 isformed on the hard mask 200 a. The small-diameter resist pattern 102 hasthe opening 102 a that does not overlap the first interconnect 12 butexposes the top of the second interconnect 22 within the area where thelarge-diameter concave portion 41-4 is formed in the bonded substrate.

As illustrated in FIG. 5E, the pattern of a small-diameter concaveportion 42-4 is formed in the substrate having the filling member 400filled therein by etching using the small-diameter resist pattern 102 asa mask. At this time, the filling member 400 is etched using thesmall-diameter resist pattern 102 as a mask, and the etching isterminated before the second interconnect 22 is reached. Here, etchingis performed until the unetched thickness ‘a’ on top of the firstinterconnect 12 and the unetched thickness ‘b’ on top of the secondinterconnect 22 agree (i.e., a=b). Therefore, the interlayer insulatingfilm 14 is etched as necessary.

As illustrated in FIG. 5F, the resist pattern (102) is removed. As aresult, the filling member 400 is provided in the large-diameter concaveportion 41-4, the small-diameter concave portion 42-4 is provided in thefilling member 400, and the hard mask 200 a is provided on the frontside 11 a of the semiconductor layer 11. The same mask 200 is alignedwith the opening of the large-diameter concave portion 41-4. In thiscondition, the unetched thickness ‘a’ on top of the first interconnect12 and the unetched thickness ‘b’ on top of the second interconnect 22agree (i.e., a=b).

As illustrated in FIG. 5G, the bottoms of the filling member 400 andsmall-diameter concave portion 42-4 are dug at the same time by etchingfrom above the hard mask 200 a. At this time, the filling member 400,interlayer insulating film 14 and joint section 30 are etched until bothof the first and second interconnects 12 and 22 are exposed. Here,etching is performed under the conditions that allow digging of thefilling member 400, interlayer insulating film 14 and joint section 30at the same etch rate. For example, etching is performed usingC₄F₈/Ar/O₂ as an etching gas. After the etching, the hard mask 200 a isremoved as necessary.

This completes the fabrication of the connection hole 40 having thefirst and second interconnects 12 and 22 exposed at its bottom.

As illustrated in FIG. 5H, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40.

As a result of the above steps, the manufacture of the semiconductordevice 1 according to the fourth embodiment is complete.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the Fourth Embodiment

In the manufacturing method according to the fourth embodiment describedabove, the small-diameter concave portion 42-4 is provided in thefilling member 400 without exposing the first and second interconnects12 and 22 as illustrated in FIG. 5F. At this time, etching is performedso that the unetched thickness ‘a’ on top of the first interconnect 12and the unetched thickness ‘b’ on top of the second interconnect 22agree (i.e., a=b). In this condition, the filling member 400, interlayerinsulating film 14 and joint section 30 are etched at the same etchrate. As a result, the etching is terminated when the secondinterconnect 22 is exposed simultaneously with the exposure of the firstinterconnect 12. This ensures that the exposed first interconnect 12 isnot subjected to an etching atmosphere for an extended period of time,thus minimizing excessive etching of the first interconnect 12.

Therefore, the manufacturing method according to the fourth embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40as does the manufacturing method according to the first embodiment.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

This contributes to improved yield of the semiconductor device 1.

Further, filling the filling member 400 into the large-diameter concaveportion 41-4 is a distinctive feature of the manufacturing methodaccording to the fourth embodiment. This makes it possible to form aresist film on a planarized surface made up of the surface of thefilling member 400 and that of the hard mask 200 a during the formationof the small-diameter resist pattern 102 on the hard mask 200 a asillustrated in FIG. 5D. The resist film free from level difference ispatterned by lithography. This provides improved patterning accuracy informing the small-diameter resist pattern 102 even for a small concaveportion.

This contributes to further pitch reduction in the semiconductor device.

6. Fifth Embodiment (Manufacturing Method in Which a Resist MaterialUsed to Cover the Second Interconnect is Left Unremoved in theSmall-Diameter Concave Portion Formed Earlier)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to a fifth embodiment with reference tothe cross-sectional process diagrams shown in FIGS. 6A to 6F. It shouldbe noted that the final configuration of the semiconductor device 1 isthe same as that of the semiconductor device 1 according to the firstembodiment.

First, a bonded substrate is fabricated which has the first and secondsubstrates 10 and 20 bonded together with the joint section 30sandwiched therebetween.

Next, as illustrated in FIG. 6A, the small-diameter resist pattern 102is formed on the front side 11 a of the semiconductor layer 11 of thefabricated bonded substrate. The small-diameter resist pattern 102 hasthe opening 102 a that exposes the top of the second interconnect 22.

As illustrated in FIG. 6B, the pattern of a small-diameter concaveportion 42-5 is formed on the bonded substrate by etching using thesmall-diameter resist pattern 102 as a mask. At this time, thesemiconductor layer 11, interlayer insulating film 14 and joint section30 are etched in this order using the small-diameter resist pattern 102as a mask, and the etching is terminated when the second interconnect 22is exposed. After the etching, the small-diameter resist pattern 102 isremoved.

As a result of the above, the small-diameter concave portion 42-5 isformed which has the second interconnect 22 exposed at its bottom.

As illustrated in FIG. 6C, the large-diameter resist pattern 100 isformed on the front side 11 a of the semiconductor layer 11. Thelarge-diameter resist pattern 100 has the opening 100 a that exposes thetops of the first and second interconnects 12 and 22 within the areaincluding the opening of the small-diameter concave portion 42-5 thathas been formed. During the formation of the large-diameter resistpattern 100, a resist material 100 b is left unremoved that covers thesecond interconnect 22 exposed in the small-diameter concave portion42-5.

As illustrated in FIG. 6D, the pattern of a large-diameter concaveportion 41-5 is formed on the bonded substrate by etching using thelarge-diameter resist pattern 100 as a mask. At this time, thesemiconductor layer 11, interlayer insulating film 14 and joint section30 are etched in this order using the large-diameter resist pattern 100as a mask, and the etching is terminated when the first interconnect 12is exposed. During this etching adapted to form the large-diameterconcave portion 41-5, the resist material 100 b left unremoved in thesmall-diameter concave portion 42-5 is etched and thinned. At the end ofthe etching, the resist material 100 b may be completely removed.Alternatively, some thereof may be left unremoved.

As a result of the above, the large-diameter concave portion 41 isformed which has an opening sized to overlap the first and secondinterconnects 12 and 22, with the first interconnect 12 exposed in partof the bottom.

As illustrated in FIG. 6E, the resist pattern 100 (shown in FIG. 6D) isremoved. At this time, the resist material 100 b (shown in FIG. 6D) isremoved at the same time if any is left. This completes the fabricationof the connection hole 40 having the first and second interconnects 12and 22 exposed at its bottom.

As illustrated in FIG. 6F, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40.

As a result of the above steps, the manufacture of the semiconductordevice 1 according to the fifth embodiment is complete.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the Fifth Embodiment

In the manufacturing method according to the fifth embodiment describedabove, the small-diameter concave portion 42-5 is formed first to exposethe second interconnect 22, and then the large-diameter concave portion41-5 is formed to expose the first interconnect 12, thus ensuring thatthe first interconnect 12 is not excessively etched.

Further, when the large-diameter resist pattern 100 is formed to formthe pattern of the large-diameter concave portion 41-5, the secondinterconnect 22 exposed at the bottom of the small-diameter concaveportion 42-5 is covered with the resist material 100 b. With the secondinterconnect 22 covered as described above, etching is performed usingthe large-diameter resist pattern 100 as a mask until the firstinterconnect 12 is exposed. During this period of time, the resistmaterial 100 b covering the second interconnect 22 is etched andthinned. However, the resist material 100 b is left unremoved all theway to the end of the etching or at least halfway through the etching,thus minimizing excessive etching of the second interconnect 22.

Therefore, the manufacturing method according to the fifth embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40as does the manufacturing method according to the first embodiment.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

This contributes to improved yield of the semiconductor device 1.

Further, in the manufacturing method according to the fifth embodiment,the etching from the front side 11 a of the semiconductor layer 11 tothe first interconnect 12 is performed in a single step without stoppinghalfway as illustrated in FIG. 6D, thus exposing the same interconnect12. In contrast, in the manufacturing methods according to the second tofourth embodiments, etching is stopped halfway before the firstinterconnect 12 is reached, and etching is performed again to expose thesame interconnect 12. That is, the etching from the front side 11 a ofthe semiconductor layer 11 to the first interconnect 12 is performed intwo steps, thus exposing the first interconnect 12. Therefore, themanufacturing method according to the fifth embodiment allows formanufacture of the semiconductor device 1 through a smaller number ofsteps than the manufacturing methods according to the second to fourthembodiments.

7. Sixth Embodiment (Manufacturing Method in Which Etching is StoppedHalfway in Such a Manner That the Unetched Thicknesses on Top of theFirst and Second Interconnects Agree)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to a sixth embodiment with reference tothe cross-sectional process diagrams shown in FIGS. 7A to 7F. It shouldbe noted that the final configuration of the semiconductor device 1 isthe same as that of the semiconductor device 1 according to the firstembodiment.

First, a bonded substrate is fabricated which has the first and secondsubstrates 10 and 20 bonded together with the joint section 30sandwiched therebetween.

Next, as illustrated in FIG. 7A, the small-diameter resist pattern 102is formed on the front side 11 a of the semiconductor layer 11 of thefabricated bonded substrate. The small-diameter resist pattern 102 hasthe opening 102 a that exposes the top of the second interconnect 22.

As illustrated in FIG. 7B, the pattern of a small-diameter concaveportion 42-6 is formed in the bonded substrate by etching using thesmall-diameter resist pattern 102 as a mask. At this time, thesemiconductor layer 11 and interlayer insulating film 14 are etched inthis order using the small-diameter resist pattern 102 as a mask, andthe etching is terminated before the second interconnect 22 is reached.Here, etching is performed until the unetched thickness ‘a’ on top ofthe first interconnect 12 and the unetched thickness ‘b’ on top of thesecond interconnect 22 agree (i.e., a=b). After the etching, thesmall-diameter resist pattern 102 is removed.

As a result of the above, the small-diameter concave portion 42-6 isformed in which the unetched thickness ‘a’ on top of the firstinterconnect 12 and the unetched thickness ‘b’ on top of the secondinterconnect 22 agree (i.e., a=b).

As illustrated in FIG. 7C, the large-diameter resist pattern 100 isformed anew on the front side 11 a of the semiconductor layer 11. Thelarge-diameter resist pattern 100 has the opening 100 a that exposes thetops of the first and second interconnects 12 and 22 within the areaincluding the small-diameter concave portion 42-6 that has been formed.

As illustrated in FIG. 7D, the pattern of a large-diameter concaveportion 41-6 is formed in the bonded substrate, and the bottom of thesmall-diameter concave portion 42-6 is dug, by etching using thelarge-diameter resist pattern 100 as a mask. At this time, thesemiconductor layer 11, interlayer insulating film 14 and joint section30 are etched using the large-diameter resist pattern 100 as a maskuntil both of the first and second interconnects 12 and 22 are exposed.Here, etching is performed under the conditions that allow digging ofthe semiconductor layer 11, interlayer insulating film 14 and jointsection 30 at the same etch rate.

As a result of the above, the large-diameter concave portion 41-6 isformed which has an opening sized to overlap the first and secondinterconnects 12 and 22, with the first interconnect 12 exposed in partof the bottom. At the same time, the second interconnect is exposed atthe bottom of the small-diameter concave portion 42-6.

As illustrated in FIG. 7E, the resist pattern (100) is removed. Thiscompletes the fabrication of the connection hole 40 having the first andsecond interconnects 12 and 22 exposed at its bottom.

As illustrated in FIG. 7F, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40.

As a result of the above steps, the manufacture of the semiconductordevice 1 according to the sixth embodiment is complete.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the Sixth Embodiment

In the manufacturing method according to the sixth embodiment describedabove, the small-diameter concave portion 42-6 is formed withoutexposing the first and second interconnects 12 and 22 as illustrated inFIG. 7B. At this time, etching is performed so that the unetchedthickness ‘a’ on top of the first interconnect 12 and the unetchedthickness ‘b’ on top of the second interconnect 22 agree (i.e., a=b). Asa result, the etching is terminated when the second interconnect 22 isexposed simultaneously with the exposure of the first interconnect 12.This ensures that the exposed first interconnect 12 is not subjected toan etching atmosphere for an extended period of time.

Therefore, the manufacturing method according to the sixth embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40as does the manufacturing method according to the first embodiment.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

This contributes to improved yield of the semiconductor device 1.

Further, in the manufacturing method according to the sixth embodiment,the etching from the front side 11 a of the semiconductor layer 11 tothe first interconnect 12 is performed in a single step without stoppinghalfway as illustrated in FIG. 7D, thus exposing the same interconnect12. Therefore, the manufacturing method according to the sixthembodiment allows for manufacture of the semiconductor device 1 througha smaller number of steps than the manufacturing methods according tothe second to fourth embodiments.

8. Seventh Embodiment (Manufacturing Method in Which Etching is StoppedHalfway in Such a Manner That the Unetched Thicknesses on Top of theFirst and Second Interconnects Agree and in Which a Hard Mask is Used)

A description will be given below of the manufacturing method of thesemiconductor device 1 according to a seventh embodiment with referenceto the cross-sectional process diagrams shown in FIGS. 8A to 8F. Itshould be noted that the final configuration of the semiconductor device1 is the same as that of the semiconductor device 1 according to thefirst embodiment.

First, a bonded substrate is fabricated which has the first and secondsubstrates 10 and 20 bonded together with the joint section 30sandwiched therebetween.

Next, as illustrated in FIG. 8A, the hard mask layer 200 made, forexample, of titanium nitride (TiN) is formed on the front side 11 a ofthe semiconductor layer 11 of the fabricated bonded substrate. Next, thesmall-diameter resist pattern 102 is formed on the hard mask layer 200.The same pattern 102 has the opening 102 a that exposes the top of thesecond interconnect 22.

As illustrated in FIG. 8B, the pattern of a small-diameter concaveportion 42-7 is formed on the bonded substrate by etching using thesmall-diameter resist pattern 102 as a mask. At this time, the hard masklayer 200, semiconductor layer 11 and interlayer insulating film 14 areetched in this order using the small-diameter resist pattern 102 as amask, and the etching is terminated before the second interconnect 22 isreached. Here, etching is performed until the unetched thickness ‘a’ ontop of the first interconnect 12 and the unetched thickness ‘b’ on topof the second interconnect 22 agree (i.e., a=b). After the etching, thesmall-diameter resist pattern 102 is removed.

As a result of the above, the small-diameter concave portion 42-7 isformed in which the unetched thickness ‘a’ on top of the firstinterconnect 12 and the unetched thickness ‘b’ on top of the secondinterconnect 22 agree (i.e., a=b).

As illustrated in FIG. 8C, the large-diameter resist pattern 100 isformed anew on the hard mask layer 200. The large-diameter resistpattern 100 has the opening 100 a that exposes the tops of the first andsecond interconnects 12 and 22 within the area including thesmall-diameter concave portion 42-6 that has been formed. Here, duringthe formation of the large-diameter resist pattern 100, the resist filmwith a large level difference is patterned by photolithography.Therefore, the resist material 100 b may be left unremoved near thebottom in the small-diameter concave portion 42-7. Next, the hard masklayer 200 is etched using the large-diameter resist pattern 100 as amask, thus forming the hard mask (200 a).

As illustrated in FIG. 8D, the resist pattern (100) is removed. At thistime, the resist material (100 b) left unremoved in the small-diameterconcave portion 42-7 is removed at the same time. This exposes the hardmask 200 a on the front side 11 a of the semiconductor layer 11. Thehard mask 200 a has an opening that exposes the tops of the first andsecond interconnects 12 and 22.

As illustrated in FIG. 8E, the pattern of a large-diameter concaveportion 41-7 is formed on the bonded substrate, and the bottom of thesmall-diameter concave portion 42-7 is dug, by etching using the hardmask 200 a as a mask. At this time, the semiconductor layer 11,interlayer insulating film 14 and joint section 30 are etched using thehard mask 200 a as a mask until both of the first and secondinterconnects 12 and 22 are exposed. Here, etching is performed underthe conditions that allow digging of the semiconductor layer 11,interlayer insulating film 14 and joint section 30 at the same etchrate. After the etching, the hard mask 200 a is removed as necessary.

As a result of the above, the large-diameter concave portion 41-7 isformed which has an opening sized to overlap the first and secondinterconnects 12 and 22, with the first interconnect 12 exposed in partof the bottom, thus completing the fabrication of the connection hole40.

As illustrated in FIG. 8F, the filling metal 43 made, for example, ofcopper is filled into the connection hole 40 as a conductive member,thus connecting the first and second interconnects 12 and 22 located atdifferent depths via the connection hole 40 having the filling metal 43filled therein. It should be noted that although the filling metal 43 isused here as a conductive member, the conductive member is not limitedthereto. Instead, a conductive film may be formed on the inner wall ofthe connection hole 40.

As a result of the above steps, the manufacture of the semiconductordevice 1 according to the seventh embodiment is complete.

Advantageous Effect of the Manufacturing Method of the SemiconductorDevice According to the Seventh Embodiment

In the manufacturing method according to the seventh embodimentdescribed above, the small-diameter concave portion 42-7 is formedwithout exposing the first and second interconnects 12 and 22 asillustrated in FIG. 8B. At this time, etching is performed so that theunetched thickness ‘a’ on top of the first interconnect 12 and theunetched thickness ‘b’ on top of the second interconnect 22 agree (i.e.,a=b). As a result, the etching is terminated when the secondinterconnect 22 is exposed simultaneously with the exposure of the firstinterconnect 12. This ensures that the exposed first interconnect 12 isnot subjected to an etching atmosphere for an extended period of time.

Therefore, the manufacturing method according to the seventh embodimentprevents accumulation of reaction products produced by excessive etchingof the first interconnect 12 on the side wall of the connection hole 40as does the manufacturing method according to the first embodiment.Further, the thinning of the first interconnect 12 due to excessiveetching can be prevented, thus providing proper conductivity of thefirst interconnect 12 and proper connection between the firstinterconnect 12 and filling metal 43.

This contributes to improved yield of the semiconductor device 1.

Further, in the manufacturing method according to the seventhembodiment, etching is performed using the hard mask 200 a rather thanthe large-diameter resist pattern 100 to form the pattern of thelarge-diameter concave portion 41-7 as illustrated in FIG. 8D. As aresult, even if the resist material 100 b is left unremoved that coversthe second interconnect 22 in the small-diameter concave portion 42-7formed earlier during the formation of the large-diameter resist pattern100, etching adapted to form the pattern of the large-diameter concaveportion 41-7 can be performed thereafter without a hitch as illustratedin FIG. 8C. That is, before the formation of the pattern of thelarge-diameter concave portion 41-7, the large-diameter resist pattern100 is removed. At the same time, the resist material 100 b leftunremoved is removed. Then, the pattern of the large-diameter concaveportion 41-7 is formed using the hard mask 200 a. Therefore, it is notnecessary to consider the lithography accuracy in relation to theunderlying layer with a large level difference in forming thelarge-diameter resist pattern 100, thus making it easy to set thelithography conditions.

Further, in the manufacturing method according to the seventhembodiment, the etching from the front side 11 a of the semiconductorlayer 11 to the first interconnect 12 is performed in a single stepwithout stopping halfway as illustrated in FIG. 8E, thus exposing thesame interconnect 12. As with the manufacturing method according to thefifth embodiment, therefore, the manufacturing method according to theseventh embodiment allows for manufacture of the semiconductor device 1through a smaller number of steps than the manufacturing methodsaccording to the second to fourth embodiments.

It should be noted that, in the seventh embodiment, the hard mask 200 ais formed by etching using the large-diameter resist pattern 100 as amask after the formation of the small-diameter concave portion 42-7 asillustrated in FIG. 8C. However, the manufacturing method according tothe seventh embodiment is not limited thereto. For example, the hardmask 200 a may be formed before the small-diameter concave portion 42-7is formed. At this time, the large-diameter resist pattern 100 is formedon the hard mask layer 200 first, followed by etching, thus forming thehard mask 200 a. Then, the large-diameter resist pattern 100 is removed,followed by the formation of the new resist pattern 102, thus formingthe small-diameter concave portion 42-7.

In the manufacturing methods according to the second to fourth andseventh embodiments, the following case has been described. That is, theunetched thickness ‘a’ on top of the first interconnect 12 and theunetched thickness ‘b’ on top of the second interconnect 22 are adjustedso that these thicknesses agree (i.e., a=b). In this condition, even ifthe films remaining on top of the first and second interconnects 12 and22 by etching are made of different materials, etching is performedunder the conditions that allow digging of these films at the same etchrate. The first and second interconnects 12 and 22 are exposed at thesame time, then the etching is terminated.

However, the manufacturing methods according to the second to fourth andseventh embodiments are also applicable when the etch rates of the filmsremaining unremoved on top of the first and second interconnects 12 and22 are different. In this case, it is only necessary to adjust twoperiods of time, i.e., time period ‘A’ indicating how long the filmremaining on top of the first interconnect 12 is etched before the sameinterconnect 12 is exposed and time period ‘B’ indicating how long thefilm remaining on top of the second interconnect 22 is etched before thesame interconnect 22 is exposed, by factoring in the difference in etchrate between the films so that the time periods ‘A’ and ‘B’ are equal.That is, it is only necessary to adjust the unetched thicknesses ‘a’ and‘b’ so that the time periods ‘A’ and ‘B’ are equal. These steps alsoprovide the same advantageous effect as in the manufacturing methodsaccording to the second to fourth and seventh embodiments.

In each of the above embodiments, a description has been given of theconfiguration and manufacturing method of the semiconductor devicehaving the connection hole 40 in which the single first interconnect 12is exposed together with the interlayer insulating film 14 at the bottomof the large-diameter concave portion 41, with the single secondinterconnect 22 exposed at the bottom of the small-diameter concaveportion 42. The same portion 42 is provided by digging into the bottomof the large-diameter concave portion 41.

However, the present technology is not limited in application only tothese configurations. Instead, the present technology is applicable to aconfiguration in which the plurality of first interconnects 12 areexposed together with the interlayer insulating film 14 at the bottom ofthe large-diameter concave portion 41 or to a configuration in which theplurality of second interconnects 22 are exposed at the bottom of thesmall-diameter concave portion 42.

It is possible to manufacture the semiconductor device 1 having any ofthese configurations by the same manufacturing method, thus providingthe same advantageous effect.

Further, the present technology is applicable to a configuration inwhich the large-diameter concave portion 41 has its bottoms formed attwo different depths, with the first interconnect 12 exposed at each ofthe depths.

Even the semiconductor device having such a configuration can bemanufactured by the same manufacturing method. The first interconnect 12is exposed together with the interlayer insulating film 14 only at thedeepest position of the bottom of the large-diameter concave portion 41,and the shallow bottom includes only the first interconnect 12. Even insuch a case, the first interconnect 12 exposed on the shallow bottom ofthe large-diameter concave portion 41 is excessively etched in somedegree. However, it is possible to prevent the same interconnect 12 frombeing affected by the etching adapted to expose the second interconnect22 located at a deeper position, thus providing the same advantageouseffect.

It should be noted that the present technology is also applicable to aconfiguration in which the small-diameter concave portion 42 has itsbottoms formed at two different depths, with the second interconnect 22exposed at each of the depths. The semiconductor device having such aconfiguration can be manufactured by the same manufacturing method.

Further, in each of the above embodiments, a description has been givenof the configuration and manufacturing method of the semiconductordevice having the connection hole 40 in which the first interconnect 12arranged on the first substrate 10 and the second interconnect 22arranged on the second substrate 22 are exposed.

However, the present technology is not limited in application only tothese configurations. Instead, the present technology is applicable to aconfiguration in which the first interconnect and the secondinterconnect arranged deeper than the first interconnect in a singlesemiconductor layer are exposed in a connection hole.

It is possible to manufacture the semiconductor device 1 having such aconfiguration by the same manufacturing method, thus providing the sameadvantageous effect.

While a case has been described in the above embodiments in which thefirst and second conductive layers are interconnects, the presenttechnology is not limited in application only to such a configuration.Instead, for example, the first and second conductive layers may bediffusion layers formed in a semiconductor layer. Even in this case, thepresent technology provides the same advantageous effect.

It should be noted that the present technology may have the followingconfigurations.

(1)

A semiconductor device including:

a substrate having a first conductive layer and a second conductivelayer arranged deeper than the first conductive layer;

a large-diameter concave portion having, on a main side of a substrate,an opening sized to overlap the first and second conductive layers, withthe first conductive layer exposed in part of the bottom of thelarge-diameter concave portion;

a small-diameter concave portion extended from the large-diameterconcave portion and formed by digging into the bottom of thelarge-diameter concave portion, with the second conductive layer exposedat the bottom of the small-diameter concave portion; and

a conductive member provided in a connection hole made up of the large-and small-diameter concave portions to connect the first and secondconductive layers.

(2)

The semiconductor device of feature 1, in which

the substrate is a bonded substrate having a substrate including thefirst conductive layer and a substrate including the second conductivelayer bonded together.

(3)

A manufacturing method of a semiconductor device including:

forming, on a main side of a substrate having a first conductive layerand a second conductive layer arranged deeper than the first conductivelayer, a large-diameter resist pattern having an opening that exposesthe tops of the first and second conductive layers;

forming, in the substrate, a large-diameter concave portion having thefirst conductive layer exposed at the bottom based on etching using thelarge-diameter resist pattern as a mask;

forming, on the main side of the substrate, a small-diameter resistpattern having an opening that exposes the top of the second conductivelayer within the area where the large-diameter concave portion isformed; and

forming, in the substrate, a small-diameter concave portion having thesecond conductive layer exposed at the bottom based on etching using thesmall-diameter resist pattern as a mask.

(4)

The manufacturing method of the semiconductor device of feature 3, inwhich

after the formation of the large-diameter concave portion, thesmall-diameter resist pattern is formed in such a manner as to cover thefirst conductive layer, and in which

the small-diameter concave portion is formed by etching using thesmall-diameter resist pattern as a mask.

(5)

The manufacturing method of the semiconductor device of feature 3, inwhich

the large-diameter resist pattern is formed above the substrate with ahard mask layer sandwiched therebetween, in which

before the formation of the large-diameter concave portion, a hard maskis formed by patterning the hard mask layer through etching using thelarge-diameter resist pattern as a mask, and in which

next, the small-diameter concave portion is formed by etching thesubstrate using the small-diameter resist pattern as a mask to a depthnot exposing the second conductive layer, followed by removal of thesmall-diameter resist pattern and etching from above the hard mask so asto expose the second conductive layer, and at the same time, thelarge-diameter concave portion is formed with the first conductive layerexposed therein.

(6)

The manufacturing method of the semiconductor device of feature 5, inwhich

an unetched thickness of the small-diameter concave portion on top ofthe second conductive layer agrees with an unetched thickness of thelarge-diameter concave portion on top of the first conductive layerduring etching of the substrate using the small-diameter resist patternas a mask.

(7)

The manufacturing method of the semiconductor device of feature 5 or 6,in which

after the formation of the hard mask by patterning the hard mask layerthrough etching using the large-diameter resist pattern as a mask, thesubstrate is etched to a depth not exposing the first conductive layer.

(8)

The manufacturing method of the semiconductor device of any one offeatures 5 to 7, in which

the substrate includes an interlayer insulating film and semiconductorlayer on the first conductive layer, and in which

after the formation of the hard mask by patterning the hard mask layerthrough etching using the large-diameter resist pattern as a mask, thesemiconductor layer is etched using the interlayer insulating film as anetching stopper.

(9)

The manufacturing method of the semiconductor device of feature 3, inwhich

the large-diameter resist pattern is formed above the substrate with ahard mask layer sandwiched therebetween, in which

before the formation of the large-diameter concave portion, a hard maskis formed by patterning the hard mask layer through etching using thelarge-diameter resist pattern as a mask, followed further by the etchingof the substrate to a depth not exposing the first conductive layer, inwhich

the large-diameter resist pattern is removed, and a filling member isfilled into the concave portion of the substrate for planarizationfollowed by the formation of the small-diameter resist pattern, and inwhich

the small-diameter concave portion is formed by etching the substrateusing the small-diameter resist pattern as a mask to a depth notexposing the second conductive layer, followed by removal of thesmall-diameter resist pattern and etching from above the hard mask so asto expose the second conductive layer at the bottom of thesmall-diameter concave portion, and at the same time, the large-diameterconcave portion is formed with the first conductive layer exposedtherein.

(10)

The manufacturing method of the semiconductor device of feature 3, inwhich

before the formation of the large-diameter resist pattern, thesmall-diameter concave portion is formed by etching using thesmall-diameter resist pattern as a mask, and in which

a resist material is left unremoved in the small-diameter concaveportion in such a manner as to cover the second conductive layer duringthe formation of the large-diameter resist pattern.

(11)

The manufacturing method of the semiconductor device of feature 3, inwhich

before the formation of the large-diameter resist pattern, the substrateis etched using the small-diameter resist pattern as a mask to a depthnot exposing the second conductive layer, and in which

then, the large-diameter concave portion is formed by etching using thelarge-diameter resist pattern as a mask with the first conductive layerexposed therein, and at the same time, the small-diameter concaveportion is formed with the second conductive layer exposed therein.

(12)

The manufacturing method of the semiconductor device of feature 11, inwhich

the unetched thickness of the small-diameter concave portion on top ofthe second conductive layer agrees with the unetched thickness of thelarge-diameter concave portion on top of the first conductive layerduring etching of the substrate using the small-diameter resist patternas a mask.

(13)

The manufacturing method of the semiconductor device of feature 11 or12, in which

the substrate includes the interlayer insulating film and semiconductorlayer on the first conductive layer, and in which

the semiconductor layer is etched using the interlayer insulating filmas an etching stopper during etching of the substrate using thesmall-diameter resist pattern as a mask.

(14)

The manufacturing method of the semiconductor device of any one offeatures 3 to 13, in which

after the formation of the large- and small-diameter concave portions,the conductive member connected to the first and second conductivelayers is formed in a connection hole made up of the large- andsmall-diameter concave portions.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors in so far as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A semiconductor device, comprising: a bondedsubstrate having a first conductive layer and a second conductive layerarranged deeper than the first conductive layer, wherein the bondedsubstrate includes a first substrate including the first conductivelayer and a second substrate including the second conductive layer; alarge-diameter concave portion having, on a main side of the bondedsubstrate, an opening sized to overlap at least a part of wires of thefirst conductive layer and at least a part of wires of the secondconductive layer in a plane section of the bonded substrate; asmall-diameter concave portion extended from the large-diameter concaveportion; a conductive member provided on an inner wall of a connectionhole made up of the large and small-diameter concave portions.
 2. Thesemiconductor device of claim 1, wherein the conductive member connectsa wire of the first conductive layer to a wire of the second conductivelayer.
 3. The semiconductor device of claim 1, wherein thelarge-diameter concave portion extends from the main side of the bondedsubstrate to the first conductive layer.
 4. The semiconductor device ofclaim 3, wherein the small-diameter concave portion extends from thelarge-diameter concave portion to the second conductive layer.
 5. Thesemiconductor device of claim 1, further comprising: a joint section,wherein the first substrate is bonded to the second substrate at thejoint section.
 6. The semiconductor device of claim 5, wherein the firstsubstrate is bonded to the second substrate by an adhesive.
 7. Thesemiconductor device of claim 1, further comprising: an insulating film,wherein the conductive member is in in contact with at least a portionof the insulating film.
 8. The semiconductor device of claim 1, whereinthe small-diameter concave portion is not concentric with thelarge-diameter concave portion.
 9. The semiconductor device of claim 1,wherein the conductive member is a conductive film.
 10. Thesemiconductor device of claim 1, wherein the first conductive layer isformed in a first interlayer insulating film, and wherein a portion ofthe small-diameter concave portion is formed at least partially in thefirst interlayer insulating film.
 11. The semiconductor device of claim1, wherein the first conductive layer is formed in a first interlayerinsulating film, and wherein a portion of the small-diameter concaveportion formed in the first interlayer insulating film is not defined bythe first conductive layer and is formed only in the first interlayerinsulating film.
 12. A semiconductor device, comprising: a firstsubstrate, including: a first semiconductor, the first semiconductorhaving a first surface and a second surface opposite the first surface;and a first interconnection layer, wherein the first interconnectionlayer is formed on the second surface of the first semiconductor andincludes at least a first interconnect; a second substrate, including: asecond semiconductor, the second semiconductor having a first surfaceand a second surface opposite the first surface; and a secondinterconnection layer, wherein the second interconnection layer isformed on the first surface of the second semiconductor and includes atleast a second interconnect; a joint section, wherein the firstinterconnection layer of the first substrate is joined to the secondinterconnection layer of the second substrate at the joint section; aconnection hole, including: a large diameter concave portion, whereinthe large diameter concave portion extends from the first surface of thefirst semiconductor layer to the first interconnection layer; and asmall diameter concave portion, wherein the small diameter concaveportion extends from the first interconnection layer to the secondinterconnection layer; and a conductive member, wherein the conductivemember is provided on an inner wall of the connection hole, and whereinthe conductive member connects the first interconnection layer to thesecond interconnection layer.
 13. The semiconductor device of claim 12,wherein the conductive member connects a wire of the firstinterconnection layer to a wire of the second interconnection layer. 14.The semiconductor device of claim 12, wherein the first substrate isbonded to the second substrate at the joint section.
 15. Thesemiconductor device of claim 14, wherein the first substrate is bondedto the second substrate by an adhesive.
 16. The semiconductor device ofclaim 12, further comprising: an insulating film, wherein the conductivemember is in in contact with at least a portion of the insulating film.17. The semiconductor device of claim 12, wherein the small-diameterconcave portion is not concentric with the large-diameter concaveportion.
 18. The semiconductor device of claim 12, wherein theconductive member is a conductive film.
 19. The semiconductor device ofclaim 12, wherein the first interconnection layer includes a firstinterconnect and a first interlayer insulating film, and wherein aportion of the small-diameter concave portion formed in the firstinterconnection layer is formed at least partially in the firstinterlayer insulating film.
 20. The semiconductor device of claim 12,wherein the first interconnection layer includes a first interconnectand a first interlayer insulating film, and wherein a portion of thesmall-diameter concave portion formed in the first interconnection layeris formed only in the first interlayer insulating film.